Process for producing (meth)acrolein and/or (meth)acrylic acid

ABSTRACT

A method for producing (meth)acrolein and/or (meth)acrylic acid by subjecting isobutylene and the like or propylene to a vapor-phase catalytic oxidation with molecular oxygen in the presence of a solid oxidation catalyst in a tubular type of fixed bed reactor, wherein a temperature of a hot-spot zone is sufficiently controlled and (meth)acrolein and (meth)acrylic acid are produced with a high yield.  
     A method for producing (meth)acrolein and/or (meth)acrylic acid by passing a raw material gas comprising isobutylene and the like or propylene and oxygen through a catalyst layer in a tubular type of fixed bed reactor which is filled with a solid oxidation catalyst, which includes passing a gas containing isobutylene and the like or propylene in a concentration lower than that of the raw material gas, and oxygen through the catalyst layer for a period of one hour or more prior to passing the raw material gas through the catalyst layer.

TECHNICAL FIELD

[0001] The present invention relates to a method of producingmethacrolein and/or methacrylic acid, which comprises subjectingisobutylene and/or tertiary butanol to a vapor-phase catalytic oxidationwith molecular oxygen in the presence of a solid oxidation catalyst byemploying a tubular type of fixed bed reactor.

[0002] The present invention also relates to a method of producingacrolein and/or acrylic acid, which comprises subjecting propylene tovapor-phase catalytic oxidation with molecular oxygen in the presence ofa solid oxidation catalyst by employing a tubular type of fixed bedreactor.

BACKGROUND ART

[0003] With respect to a catalyst which is used when isobutylene and/ortertiary butanol are subjected to a vapor-phase catalytic oxidation soas to produce methacrolein and/or methacrylic acid, and a catalyst whichis used when propylene is subjected to a vapor-phase catalytic oxidationso as to produce acrolein and/or acrylic acid, a number of proposalshave been made. These proposals relate primarily to elementsconstituting the catalyst and to the ratios thereof.

[0004] The above vapor-phase catalytic oxidation is an exothermicreaction, which causes thermal storage in a catalyst layer. A hightemperature local zone which results from the thermal storage isreferred to as a “hot-spot”. An excessive high temperature of this zonecauses excessive oxidation, whereby the yield of an object product isdecreased. Therefore, in the industrial operation of the aboveoxidation, the inhibition of the temperature of a hot-spot is a seriousproblem. In particular, when concentrations of isobutylene and/ortertiary butanol (which may be referred to as “isobutylene and thelike”) or propylene in a raw material gas are increased so as toincrease the productivity, the temperature of a hot-spot tends to beelevated, and therefore, reaction conditions therefor are actuallysubjected to large constraints.

[0005] Therefore, in order to industrially produce (meth)acrolein and/or(meth)acrylic acid with a high yield, it is very important to controlthe temperature of a hot-spot zone. Furthermore, in particular, when asolid oxidation catalyst including molybdenum is used, it is importantto prevent a generation of the hot-spot because the molybdenum componentis apt to easily sublimate.

[0006] Additionally, the term “(meth)acrolein” means “methacroleinand/or acrolein”, and the term “(meth)acrylic acid” means “methacrylicacid and/or acrylic acid”.

[0007] Heretofore, several methods of controlling the temperature of ahot-spot zone have been proposed. For example, JP-A-3-176440 discloses amethod which comprises filling a reactor with a plural kinds ofcatalysts, which are different from each other on activities and havebeen prepared by varying their compositions, so that the activities areincreasingly enhanced from the inlet side of a raw material gas towardthe outlet side thereof, and passing a raw material gas includingoxygen, isobutylene and the like through the catalysts layer.JP-A-55-113730 discloses a method which comprises filling a reactor witha plural kinds of catalysts, which are different from each other onactivities and have been prepared by varying their compositions, so thatthe activities are increasingly enhanced from the inlet side of a rawmaterial gas toward the outlet side thereof, and passing a raw materialgas including oxygen and propylene through the catalysts layer.JP-A-8-92147 discloses a method which comprises controlling a flow of aheating medium so that a temperature of a heating medium bath beelevated by 2° C. to 10° C. between the inlet port of a multi-tubulartype of fixed bed reactor having the heating medium bath and the outletport thereof, when propylene is subjected to a vapor-phase oxidationinto acrolein by using the reactor.

[0008] Each of these methods is the one in which the rate of reactionper unit volume at an inlet side for a raw material gas in a catalystlayer within a reactor is lowered so as to control a calorific value ofreaction per unit volume, so that the temperature of a hot-spot zone canbe lowered.

[0009] Furthermore, JP-A-2001-55355 discloses a method of producing anunsaturated nitrile and/or an unsaturated carboxylic acid, whichcomprises subjecting a hydrocarbon to a-vapor-phase catalytic oxidationin the presence of a compound metal-oxide catalyst including, as anessential ingredient(s), molybdenum, vanadium, and at least one elementselected from the group consisting of tellurium and antimony, whereinthe temperature is elevated in an atmosphere in which oxygen and/or acombustible gas are substantially included, until the temperature of thecatalyst layer reaches a temperature at which a reaction can beinitiated. Besides, in comparative example of the specification thereof,a method of elevating the temperature in an atmosphere of air is alsodisclosed.

DISCLOSURE OF INVENTION

[0010] However, there has been a problem that the temperature of ahot-spot zone can not be sufficiently controlled by merely these methodsand the yield of each of (meth)acrolein and (meth)acrylic acid is low.

[0011] It is an object of the present invention to provide a method forproducing (meth)acrolein and/or (meth)acrylic acid by subjectingisobutylene and the like or propylene to a vapor-phase catalyticoxidation with molecular oxygen in the presence of a solid oxidationcatalyst in a tubular type of fixed bed reactor, whereby a temperatureof a hot-spot zone is sufficiently controlled and (meth)acrolein and(meth)acrylic acid are produced with a high yield.

[0012] The present invention provides a method for producing(meth)acrolein and/or (meth)acrylic acid by passing a raw material gascomprising isobutylene and the like or propylene and oxygen through acatalyst layer in a tubular type of fixed bed reactor which is filledwith a solid oxidation catalyst, which comprises passing a gascomprising isobutylene and the like or propylene in a concentrationlower than that of said raw material gas, and oxygen through saidcatalyst layer for a period of one hour or more prior to passing saidraw material gas through said catalyst layer.

[0013] In particular, the present invention also provides a method forproducing (meth)acrolein and/or (meth)acrylic acid, which comprises:

[0014] filling a tubular type of fixed bed reactor with a solidoxidation catalyst;

[0015] elevating a temperature of the resultant catalyst layer to arange of 250° C. to 400° C. while passing a gas including oxygen,nitrogen, water vapor and 0 to 0.5% by volume of isobutylene and thelike or propylene through said catalyst layer; and

[0016] passing a gas including 1 to 3.8% by volume of isobutylene andthe like or propylene, 7 to 16% by volume of oxygen and 5 to 50% byvolume of water vapor through said catalyst layer at a temperature of250° C. to 400° C. for a period of one hour or more; and thereafterpassing a raw material gas including 4 to 9% by volume of isobutyleneand the like or propylene, 7 to 16% by volume of oxygen and 5 to 50% byvolume of water vapor through said catalyst layer at a temperature of250° C. to 400° C.

[0017] In the present invention, a reaction for synthesizing(meth)acrolein and/or (meth)acrylic acid is carried out by using atubular type of fixed bed reactor. The tubular type of fixed bed reactoris industrially and preferably, but not in particular limited to, amulti-tubular type of fixed bed reactor which is provided with severalthousands to several tens thousand of reaction tubes having an innerdiameter of 10 to 40 mm. Furthermore, the tubular type of fixed bedreactor is preferably the one as provided with a heating medium bath.The heating medium is not in particular limited, and includes salt meltssuch as potassium nitrate and sodium nitrite.

[0018] In the present invention, a solid oxidation catalyst to be usedis not in particular limited, provided that the catalyst is a solidcatalyst for this oxidation reaction, and a compound oxide includingmolybdenum which has been conventionally known and the like can be usedtherefor. For a reaction wherein isobutylene and the like are used asraw materials, a compound oxide as represented by the following formula(1):

Mo_(a)Bi_(b)Fe_(c)A_(d)X_(e)Y_(f)Z_(g)O_(h)  (1)

[0019] wherein Mo, Bi, Fe and O represent molybdenum, bismuth, iron andoxygen, respectively; A represents nickel and/or cobalt; X represents atleast one element selected from the group consisting of magnesium, zinc,chromium, manganese, tin and lead; Y represents at least one elementselected from the group consisting of phosphorus, boron, sulfur,tellurium, silicon, germanium, cerium, niobium, titanium, zirconium,tungsten and antimony; Z represents at least one element selected fromthe group consisting of potassium, sodium, rubidium, cesium andthallium; and each of a, b, c, d, e, f, g and h represents an atomicratio of each element, wherein 0.1≦b≦5, 0.1≦c≦5, 1≦d ≦12, 0≦e≦10, 0≦f≦10and 0.01≦g≦3 when a=12, and h means an atomic ratio of oxygen necessaryto satisfy the atomic valence of each of said elements, is preferred asa catalyst. A particularly preferred atomic ratio of each element is0.2≦b≦3, 0.5≦c≦4, 2≦d≦10 and 0.1≦g≦2 when a=12.

[0020] Besides, for a reaction wherein propylene is used as a rawmaterial, a compound oxide as represented by the following formula (2):

MO_(a′)B_(b′), Fe_(c′)A′_(d′)X′_(e′)Y′_(f′)Z′_(g′)Si_(h′)O_(i)  (2)

[0021] wherein Mo, Bi, Fe, Si and O represent molybdenum, bismuth, iron,silicon and oxygen, respectively; A′ represents nickel and/or cobalt; X′represents at least one element selected from the group consisting ofmagnesium, zinc, chromium, manganese, tin, strontium, barium, copper,silver and lead; Y′ represents at least one element selected from thegroup consisting of phosphorus, boron, sulfur, tellurium, aluminum,gallium, germanium, indium, lanthanum, cerium, niobium, tantalum,titanium, zirconium, tungsten and antimony; Z′ represents at least oneelement selected from the group consisting of potassium, sodium,rubidium, cesium and thallium; each of a′, b′, c′, d′, e′, f′, g′, h′and i represents an atomic ratio of each element, wherein 0.01≦b′≦5,0.01≦c′≦5, 1≦d′≦12, 0≦e′≦10, 0≦f′≦10, 0.001≦g′≦3 and 0≦h′≦20 when a′=12,and i means an atomic ratio of oxygen necessary to satisfy the atomicvalence of each of said elements, is preferred as a catalyst. Aparticularly preferred atomic ratio of each element is 0.1≦b′≦3,0.1≦c′≦4, 2≦d′≦10 and 0.005≦g′≦2 when a′=12.

[0022] A method of preparing the catalyst to be used in the presentinvention is not in particular limited, and various methods asconventionally well known can be used, provided that components do notcause remarkable maldistribution.

[0023] Raw materials as used for preparing the catalyst are not inparticular limited, and a nitrate, a carbonate, an acetate, an ammoniumsalt, an oxide and a halide and the like of each element can be used incombination to each other. For example, as a molybdenum raw material,ammonium paramolybdate, molybdenum trioxide, molybdenum chloride or thelike can be used.

[0024] The catalyst used in the present invention can be used with nocarrier, while the catalyst can be used in the form of a supportedcatalyst which is supported on an inactive carrier such as silica,alumina, a silica-alumina, or silicon-carbide, or in the form of acatalyst diluted with such an inactive carrier.

[0025] In the present invention, the term “a catalyst layer” means aspace zone in a reaction tube of a tubular type of fixed bed reactor,which includes at least a catalyst; that is to say, not only a spacewhich is filled with merely a catalyst but also a space in which acatalyst is diluted with an inactive carrier or the like are referred toas “a catalyst layer”. However, a space at each end as filled withnothing, or a space as filled with merely an inactive carrier or thelike are not referred to as “a catalyst layer”, because no catalyst issubstantially included therein.

[0026] A reaction for synthesizing (meth)acrolein and/or (meth)acrylicacid, which comprises subjecting isobutylene and the like or propyleneto vapor-phase catalytic oxidation with molecular oxygen in the presenceof a solid oxidation catalyst by employing a tubular type of fixed bedreactor, which is simply referred to as “an oxidation reaction”, ispreferably carried out at a reaction temperature in the range of 250° C.to 400° C. However, when a raw material gas including, for example, 4 to9% by volume of isobutylene and the like or propylene, 7 to 16% byvolume of oxygen, and 5 to 50% by volume of water vapor, which is simplyreferred to as “a raw material gas”, is passed from the initiation ofreaction through a catalyst layer whose temperature is maintained at areaction temperature of about 250° C. to about 400° C., a hot-spothaving a high maximum temperature tends to be formed near a raw materialgas inlet port of the catalyst layer.

[0027] The present inventor has made extensive studies to solve thisproblem. As a result, it has been found that according to a method forproducing (meth)acrolein and/or (meth)acrylic acid by passing a rawmaterial gas comprising isobutylene and the like or propylene, andoxygen through a catalyst layer in a tubular type of fixed bed reactorwhich is filled with a solid oxidation catalyst, which comprises passinga gas comprising isobutylene and the like or propylene in aconcentration lower than that of said raw material gas, and oxygenthrough said catalyst layer for a period of one hour or more prior topassing said raw material gas through said catalyst layer, when anoxidation reaction is carried out under usual reaction conditions, atemperature of a hot-spot zone can be sufficiently controlled, and as aresult, (meth)acrolein and/or (meth)acrylic acid can be produced with ahigh yield.

[0028] In particular, according to a method which comprises elevating atemperature of the catalyst layer to a temperature of 250° C. to 400° C.while passing a gas comprising oxygen, nitrogen, water vapor and 0 to0.5% by volume of isobutylene and the like or propylene through saidcatalyst layer; and passing a gas comprising 1 to 3.8% by volume ofisobutylene and the like or propylene, 7 to 16% by volume of oxygen and5 to 50% by volume of water vapor at a temperature of 250° C. to 400° C.through said catalyst layer for a period of one hour or more, prior topassing the above raw material gas through the catalyst layer, when anoxidation reaction is carried out under usual reaction conditions, thatis, at a reaction temperature of 250° C. to 400° C. using the above rawmaterial gas, the temperature of the hot-spot zone can be in particularsufficiently controlled.

[0029] A temperature of the catalyst layer before elevating thetemperature of the catalyst layer to the range of 250° C. to 400° C.,that is, the temperature at which the temperature-elevation is startedis not in particular limited, but is preferably in the range of 10° C.to 240° C. Furthermore, a temperature-elevation rate also is not inparticular limited, but is preferably in the range of 10 to 500°C./hour, particularly 20 to 400° C./hour.

[0030] A passing gas which is passed for elevating the temperature ofthe catalyst layer to the range of 250° C. to 400° C. is a gascomprising isobutylene and the like or propylene, and oxygen, preferablycomprising 0 to 0.5% by volume of isobutylene and the like or propylene,oxygen, nitrogen and water vapor. The concentrations of oxygen, nitrogenand water vapor in this gas are not in particular limited, butpreferably, oxygen is in the range of 1 to 21% by volume, nitrogen is inthe range of 29 to 98.5% by volume, and water vapor is in the range of0.5 to 50% by volume. Besides, isobutylene and the like or propylene isin the range of 0 to 0.5% by volume, preferably 0 to 0.3% by volume, andin particular preferably 0 to 0.1% by volume. When a gas comprisingisobutylene and the like or propylene in an amount exceeding 0.5% byvolume is passed with the temperature of the catalyst layer lower than250° C., compounds having a relatively high boiling point which isproduced on the catalyst may poison active sites of the catalyst.Incidentally, the wording “the concentration of isobutylene and thelike” means the sum of the concentration of each of isobutylene andtertiary butanol. This passing gas can include other gases in additionto oxygen, nitrogen, water vapor, and isobutylene and the like orpropylene. As such other gases, for example, an inert gas such as carbondioxide, lower saturated aldehyde, and ketone and the like can beenumerated. However, when an organic compound such as lower saturatedaldehyde is included, the sum of the concentration of each ofisobutylene and the like or propylene and other organic compounds ispreferably 0.5% by volume or less. When the temperature of the catalystlayer is elevated, the flow rate of the passing gas is not particularlylimited; however, such a flow rate to provide a space velocity of 100 to2000 hours⁻¹ is preferred. In this case, the internal pressure of thereactor is usually from atmospheric pressure to several atmosphericpressure.

[0031] The above gas which is passed through the catalyst layer afterelevating the temperature of the catalyst layer is the one including 1to 3.8% by volume of isobutylene and the like or propylene, 7 to 16% byvolume of oxygen and 5 to 50% by volume of water vapor. Theconcentration of isobutylene and the like or propylene is preferably inthe range of 1 to 3% by volume, and in particular preferably 1 to 2.5%by volume; the concentration of oxygen is preferably in the range of 7.5to 14% by volume, and in particular preferably 8 to 12% by volume; andthe concentration of water vapor is preferably in the range of 2 to 40%by volume, and in particular preferably 4 to 30% by volume. When thisgas is passed, the temperature of the gas is in the range of 250 to 400°C. Furthermore, a period of time during which the gas is passed is onehour or more, preferably 1.5 to 100 hours, and in particular preferably2 to 50 hours. This gas can include other gases in addition to oxygen,water vapor, and isobutylene and the like or propylene. As such othergases, for example, nitrogen, carbon dioxide, lower saturated aldehyde,and ketone and the like can be enumerated. The flow rate of the gaswhich is passed after elevating the temperature of the catalyst layer isnot particularly limited; however, such a flow rate to provide a spacevelocity of 100 to 3000 hour⁻¹ is preferred. In this case, the internalpressure of the reactor is usually from atmospheric pressure to severalatmospheric pressure. When the gas is passed, a hot-spot zone having alow maximum temperature is formed over a large area.

[0032] Thereafter, when an oxidation reaction is carried out under theabove reaction conditions, that is, at a reaction temperature of 250 to400° C. using a raw material gas including 4 to 9% by volume ofisobutylene and the like or propylene, the maximum temperature of thehot-spot zone is in particular restrained. As a result, sequentialoxidation on the hot-spot zone is in particular restrained, whereby(meth)acrolein and (meth)acrylic acid can be produced with a high yield.The flow rate of the raw material gas is not particularly limited;however, such a flow rate to provide a space velocity of 300 to 3000hour⁻¹, particularly 500 to 2000 hour⁻¹, is preferred. The reactiontemperature for the oxidation reaction is preferably in the range of250° C. to 400° C., and in particular preferably in the range of 280° C.to 380° C. Besides, the reaction pressure is usually from atmosphericpressure to several atmospheric pressure.

[0033] When the present invention is carried out, it is economicallyadvantageous to use air as an oxygen source for the raw material gas,the gas which is passed on elevating the temperature of a catalystlayer, and the gas which is passed after elevating the catalyst layertemperature.

BEST MODE FOR CARRYING OUT THE INVENTION

[0034] Examples will be enumerated hereinafter to more particularlyexplain the present invention. Incidentally, the unit “part(s)” inExamples and Comparative Examples means “part(s) by mass”. Thecomposition of a catalyst was calculated from the amounts of charged rawmaterials of catalyst components. As a heating medium for a reactor, asalt melt comprising 50% by mass of potassium nitrate and 50% by mass ofsodium nitrite was used. A hot-spot was detected from ΔT of a catalystlayer (i.e., the temperature of the catalyst layer minus the temperatureof a heating medium bath).

[0035] A temperature within the catalyst layer was measured by using athermocouple inserted in a protective tube which was located at a centerof a cross-section perpendicular to a tube axial direction of a reactiontube. Additionally, the inside of the protective tube was separated froma system of reaction, while the position of temperature measurementcould be shifted by adjusting the length of the thermocouple as insertedthereinto.

[0036] The analyses of a raw material gas and a product gas of reactionwere carried out by means of gas chromatography.

[0037] In addition, the rate of reaction of isobutylene and the like orpropylene, the selectivity factors of produced (meth)acrolein and(meth)acrylic acid, and the yield of (meth)acrolein and (meth)acrylicacid are defined as follows, respectively:

[0038] Rate of reaction of isobutylene and the like or propylene(%)=(B/A)×100;

[0039] Selectivity factor of (meth)acrolein (%)=(C/B)×100;

[0040] Selectivity factor of (meth)acrylic acid (%)=(D/B)×100; and

[0041] Yield of (meth)acrolein and (meth)acrylic acid(%)={(C+D)/A)}×100,

[0042] wherein A represents the number of moles of fed isobutylene andthe like or propylene; B represents the number of moles of reactedisobutylene and the like or propylene; C represents the number of molesof produced (meth)acrolein; and D represents the number of moles ofproduced (meth)acrylic acid.

EXAMPLE 1

[0043] To 1000 parts of water, 500 parts of ammonium paramolybdate, 18.5parts of ammonium paratungstate, 18.4 parts of cesium nitrate and 354.5parts of silicasol of 20% by mass were added, heated and agitated(Liquid A). Aside from this, to 850 parts of water, 250 parts of nitricacid of 60% by mass were added and homogenized, and then 57.2 parts ofbismuth nitrate was added thereto and dissolved. To the mixture, 238.4parts of ferric nitrate, 4.7 parts of chromium(III) nitrate, 411.8 partsof nickel(II) nitrate and 60.5 parts of magnesium nitrate weresequentially added, and dissolved (Liquid B). Liquid B was added toLiquid A into a slurry, and then 34.4 parts of antimony trioxide wereadded thereto and heated and agitated, so that most of water wasevaporated. The resultant caked matter was dried at a temperature of120° C., and then calcined at a temperature of 500° C. for a period ofsix hours. To 100 parts of the resultant calcined product, 2 parts ofgraphite were added, which were then formed into rings having an outerdiameter of 5 mm, an inner diameter of 2 mm and a length of 5 mm byusing a tablet forming machine, whereby Catalyst 1 was obtained. Theelementary composition of Catalyst 1 comprisedMo₁₂Bi_(0.5)Fe_(2.5)Ni₆Mg₁Cr_(0.05)W_(0.3)Sb₁Si₅Cs_(0.4), except oxygen.

[0044] The temperature of a heating medium bath of a tubular type offixed bed steel reactor having an inner diameter of 25.4 mm with theheating medium bath was set to a temperature of 180° C., and an inletside for raw material gas was filled with a mixture of 620 ml ofCatalyst 1 and 130 ml of a spherical alumina having an outer diameter of5 mm, while an outlet side was filled with 750 ml of Catalyst 1, whereinthe length of a catalyst layer was 3005 mm.

[0045] The heating medium bath temperature was elevated to a temperatureof 340° C. at a rate of 50° C./hour, while a gas comprising 9% by volumeof oxygen, 10% by volume of water vapor and 81% by volume of nitrogenwas passed through this catalyst layer at a space velocity of 240hour⁻¹.

[0046] Then, with the heating medium bath temperature maintained at atemperature of 340° C., a gas (i. e., a passing gas after elevating thetemperature) comprising 2% by volume of isobutylene, 8% by volume ofoxygen, 15% by volume of water vapor and 75% by volume of nitrogen waspassed through the catalyst layer at a space velocity of 1000 hours⁻¹for a period of three hours.

[0047] Subsequently, with the heating medium bath temperature maintainedat a temperature of 340° C., a raw material gas comprising 5% by volumeof isobutylene, 12% by volume of oxygen, 10% by volume of water vaporand 73% by volume of nitrogen was passed through the catalyst layer at areaction temperature (i. e., a heating medium bath temperature) of 340°C. at a space velocity of 1000 hour⁻¹. When the temperatures of thecatalyst layer were measured at this time, a hot spot having a maximumtemperature was observed at a site located 500 mm apart from the end ofthe inlet side for the raw material gas, wherein ΔT at the maximumtemperature was 33° C. In addition, the rate of reaction of isobutylenewas 95.5%, the selectivity factor of methacrolein was 85.7%, theselectivity factor of methacrylic acid was 3.6%, and the yield ofmethacrolein and methacrylic acid was 85.3%.

EXAMPLE 2

[0048] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the composition of a passing gas afterelevating the temperature was changed to the one comprising 2.6% byvolume of isobutylene, 8% by volume of oxygen, 15% by volume of watervapor and 74.4% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 470 mm apart from theend of the raw material gas inlet side of a catalyst layer, wherein ΔTat the maximum temperature was 35° C. In addition, the rate of reactionof isobutylene was 95.6%, the selectivity factor of methacrolein was85.4%, the selectivity factor of methacrylic acid was 3.6%, and theyield of methacrolein and methacrylic acid was 85.1%.

EXAMPLE 3

[0049] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the time for passing the passing gas afterelevating the temperature was changed to 1.5 hours. As a result, a hotspot having a maximum temperature was observed at a site located 470 mmapart from the end of the raw material gas inlet side of a catalystlayer, wherein ΔT at the maximum temperature was 35° C. In addition, therate of reaction of isobutylene was 95.7%, the selectivity factor ofmethacrolein was 85.3%, the selectivity factor of methacrylic acid was3.6%, and the yield of methacrolein and methacrylic acid was 85.1%.

COMPARATIVE EXAMPLE 1

[0050] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the temperature of a heating medium bath waselevated to 340° C. without passing the passing gas after elevating thetemperature, and except that thereafter a raw material gas wasimmediately passed through the catalyst layer. As a result, a hot spothaving a maximum temperature was observed at a site located 400 mm apartfrom the end of the raw material gas inlet side of the catalyst layer,wherein ΔT at the maximum temperature was 45° C. In addition, the rateof reaction of isobutylene was 94.3%, the selectivity factor ofmethacrolein was 83.1%, the selectivity factor of methacrylic acid was3.7%, and the yield of methacrolein and methacrylic acid was 81.9%.

COMPARATIVE EXAMPLE 2

[0051] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the time for passing the passing gas afterelevating the temperature was changed to ten minutes. As a result, a hotspot having a maximum temperature was observed at a site located 400 mmapart from the end of the raw material gas inlet side of the catalystlayer, wherein ΔT at the maximum temperature was 44° C. In addition, therate of reaction of isobutylene was 94.4%, the selectivity factor ofmethacrolein was 83.2%, the selectivity factor of methacrylic acid was3.7%, and the yield of methacrolein and methacrylic acid was 82.0%.

COMPARATIVE EXAMPLE 3

[0052] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 4.5% byvolume of isobutylene, 12% by volume of oxygen, 10% by volume of watervapor and 73.5% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 400 mm apart from theend of the raw material gas inlet side of a catalyst layer, wherein ΔTat this maximum temperature was 45° C. In addition, the rate of reactionof isobutylene was 94.3%, the selectivity factor of methacrolein was83.1%, the selectivity factor of methacrylic acid was 3.7%, and theyield of methacrolein and methacrylic acid was 81.9%.

COMPARATIVE EXAMPLE 4

[0053] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 0.6% byvolume of isobutylene, 8% by volume of oxygen, 15% by volume of watervapor and 76.4% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 400 mm apart from theend of the raw material gas inlet side of the catalyst layer, wherein ΔTat this maximum temperature was 44° C. In addition, the rate of reactionof isobutylene was 94.4%, the selectivity factor of methacrolein was83.2%, the selectivity factor of methacrylic acid was 3.7%, and theyield of methacrolein and methacrylic acid was 82.0%.

COMPARATIVE EXAMPLE 5

[0054] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the composition of the gas as passed when thetemperature of a heating medium bath was elevated to 340° C. was changedto the one comprising 2% by volume of isobutylene, 8% by volume ofoxygen, 15% by volume of water vapor and 75% by volume of nitrogen. As aresult, a hot spot having a maximum temperature was observed at a sitelocated 550 mm apart from the end of the raw material gas inlet side ofa catalyst layer, wherein ΔT at this maximum temperature was 31° C. Inaddition, the rate of reaction of isobutylene was 92.2%, the selectivityfactor of methacrolein was 85.8%, the selectivity factor of methacrylicacid was 3.4%, and the yield of methacrolein and methacrylic acid was82.2%. From the results, it is considered that the catalyst was poisonedwhen the temperature thereof was elevated, because ΔT at the hot spotwas decreased as compared to the one in Example 1 while the rate ofreaction of isobutylene also was decreased.

EXAMPLE 4

[0055] To 400 parts of water, 42 parts of 60% nitric acid were added toform a homogeneous solution, to which 68.7 parts of bismuth nitrate wasthen added and dissolved. 102.9 parts of nickel nitrate and 24.1 partsof antimony trioxide were sequentially added thereto. To this mixedliquid, 165 parts of 28% aqueous ammonia was added so as to obtain awhite precipitate and a blue supernatant. These were heated and agitatedso as to evaporate most of water. The resultant slurry was dried at atemperature of 120° C. for a period of 16 hours, and then heat-treatedat a temperature of 750° C. for a period of two hours, and pulverized soas to obtain fine powder of a bismuth-nickel-antimony compound.

[0056] To 1000 parts of water, 500 parts of ammonium paramolybdate, 12.3parts of ammonium paratungstate and 23.0 parts of cesium nitrate wereadded, heated and agitated (Liquid C). Aside from this, to 700 parts ofwater, 230.8 parts of ferric nitrate, 418.9 parts of cobalt nitrate and60.5 parts of magnesium nitrate were sequentially added and dissolved(Liquid D). Liquid D was added to Liquid C to form a slurry, to which425.5 parts of 20% silica-sol and the above-mentionedbismuth-nickel-antimony compound fine powder were then added, heated andagitated, so that most of water was evaporated. The resultant cakedmatter was dried at a temperature of 130° C., and then calcined at atemperature of 300° C. in an air atmosphere for a period of one hour,and pulverized. To 100 parts of the resultant pulverized product, 2parts of graphite were added and mixed. The mixture were formed intorings having an outer diameter of 5 mm, an inner diameter of 2 mm and alength of 3 mm by using a tablet forming machine. This formed tabletproduct was calcined at a temperature of 520° C. for a period of threehours while air was passed, whereby Catalyst 2 was obtained. Theelementary composition of Catalyst 2 comprisedMo₁₂W_(0.2)Bi_(0.6)Fe_(2.4)Sb_(0.7)Ni_(1.5)Co_(6.1)Mg_(1.0)Cs_(0.5)Si_(6.0) by an atomic ratio except oxygen.

[0057] The temperature of a heating medium bath of a tubular type offixed bed steel reactor having an inner diameter of 25.4 mm as providedwith the heating medium bath was set to a temperature of 180° C., andthe inlet side for raw material gas was filled with a mixture of 620 mlof Catalyst 2 and 130 ml of a spherical alumina having an outer diameterof 5 mm, while the outlet side was filled with 750 ml of Catalyst 2,wherein the length of a catalyst layer was 3005 mm.

[0058] The heating medium bath temperature was elevated to a temperatureof 340° C. at a rate of 50° C./hour, while a gas comprising 9% by volumeof oxygen, 10% by volume of water vapor and 81% by volume of nitrogenwas passed through this catalyst layer at a space velocity of 240hour⁼¹.

[0059] Then, with the heating medium bath temperature maintained at atemperature of 340° C., a gas comprising 2% by volume of tertiarybutanol, 8% by volume of oxygen, 15% by volume of water vapor and 75% byvolume of nitrogen was passed through the catalyst layer at a spacevelocity of 1000 hour⁻¹ for a period of three hours.

[0060] Subsequently, with the heating medium bath temperature maintainedat a temperature of 340° C., a raw material gas comprising 5% by volumeof tertiary butanol, 12% by volume of oxygen, 10% by volume of watervapor and 73% by volume of nitrogen was passed through the catalystlayer at a reaction temperature (i. e., a heating medium bathtemperature) of 340° C. at a space velocity of 1000 hour⁻¹. When thetemperatures of the catalyst layer were measured at this time, a hotspot having a maximum temperature was observed at a site located 550 mmapart from the end of the inlet side for the raw material gas, whereinΔT at the maximum temperature was 32° C. In addition, the rate ofreaction of tertiary butanol was 100.0%, the selectivity factor ofmethacrolein was 84.0%, the selectivity factor of methacrylic acid was3.2%, and the yield of methacrolein and methacrylic acid was 87.2%.

COMPARATIVE EXAMPLE 6

[0061] An oxidation reaction was carried out in a similar manner to thatin Example 4, except that the temperature of a heating medium bath waselevated to 340° C. without passing the passing gas after elevating thetemperature, and except that thereafter a raw material gas wasimmediately passed through the catalyst layer. As a result, a hot spothaving a maximum temperature was observed at a site located 450 mm apartfrom the end of the raw material gas inlet side of the catalyst layer,wherein ΔT at the maximum temperature was 44° C. In addition, the rateof reaction of tertiary butanol was 100.0%, the selectivity factor ofmethacrolein was 81.7%, the selectivity factor of methacrylic acid was3.3%, and the yield of methacrolein and methacrylic acid was 85.0%.

EXAMPLE 5

[0062] To 1000 parts of water, 500 parts of ammonium paramolybdate, 6.2parts of ammonium paratungstate, 1.4 parts of potassium nitrate and212.7 parts of silicasol of 20% by mass were added, heated and agitated(Liquid A). Aside from this, to 850 parts of water, 50 parts of nitricacid of 60% by mass were added and homogenized, and then 103.0 parts ofbismuth nitrate were added thereto and dissolved. To the mixture, 114.4parts of ferric nitrate, 274.7 parts of cobalt nitrate, 34.3 parts ofnickel(II) nitrate, 7.0 parts of zinc nitrate and 30.3 parts ofmagnesium nitrate were sequentially added and dissolved (Liquid B).Liquid B was added to Liquid A to form a slurry, and then 10.3 parts ofantimony trioxide were added thereto and heated and agitated, so thatmost of water was evaporated. The resultant caked matter was dried at atemperature of 120° C., and then calcined at a temperature of 500° C.for a period of four hours. To 100 parts of the resultant calcinedproduct, 2 parts of graphite were added, which were then formed intorings having an outer diameter of 4 mm, an inner diameter of 2 mm and alength of 4 mm by using a tablet forming machine, whereby Catalyst 1 wasobtained. The elementary composition of Catalyst 1 comprisedMo₁₂W_(0.1)Bi_(0.9)Fe_(1.2)Co₄Ni_(0.5)Zn_(0.1)Mg_(0.5)Sb_(0.3)K_(0.06)Si₃,except oxygen.

[0063] The temperature of a heating medium bath of a tubular type offixed bed steel reactor having an inner diameter of 25.4 mm as providedwith the heating medium bath was set to a temperature of 180° C., andthe inlet side for raw material gas was filled with a mixture of 620 mlof Catalyst 1 and 130 ml of a spherical alumina having an outer diameterof 5 mm, while the outlet side was filled with 750 ml of Catalyst 1,wherein the length of a catalyst layer was 3005 mm.

[0064] The heating medium bath temperature was elevated to a temperatureof 310° C. at a rate of 50° C./hour, while a gas comprising 9% by volumeof oxygen, 10% by volume of water vapor and 81% by volume of nitrogenwas passed through this catalyst layer at a space velocity of 240hour⁻¹.

[0065] Then, with the heating medium bath temperature maintained at atemperature of 310° C., a gas (i. e., a passing gas after elevating thetemperature) comprising 2% by volume of propylene, 8% by volume ofoxygen, 15% by volume of water vapor and 75% by volume of nitrogen waspassed through the catalyst layer at a space velocity of 1000 hour⁻¹ fora period of three hours.

[0066] Subsequently, with the heating medium bath temperature maintainedat a temperature of 310° C., a raw material gas comprising 5% by volumeof propylene, 12% by volume of oxygen, 10% by volume of water vapor and73% by volume of nitrogen was passed through the catalyst layer at areaction temperature (i. e., a heating medium bath temperature) of 340°C. at a space velocity of 1000 hour⁻¹. When the temperatures of thecatalyst layer were measured at this time, a hot spot having a maximumtemperature was observed at a site located 500 mm apart from the end ofthe inlet side for the raw material gas, wherein ΔT at the maximumtemperature was 29° C. In addition, the rate of reaction of propylenewas 98.5%, the selectivity factor of acrolein was 88.3%, the selectivityfactor of acrylic acid was 5.8%, and the yield of acrolein and acrylicacid was 92.7%.

EXAMPLE 6

[0067] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 2.6% byvolume of propylene, 8% by volume of oxygen, 15% by volume of watervapor and 74.4% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 470 mm apart from theend of the raw material gas inlet side of a catalyst layer, wherein ΔTat the maximum temperature was 31° C. In addition, the rate of reactionof propylene was 98.6%, the selectivity factor of acrolein was 88.1%,the selectivity factor of acrylic acid was 5.8%, and the yield ofacrolein and acrylic acid was 92.6%.

EXAMPLE 7

[0068] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the time for passing the passing gas afterelevating the temperature was changed to 1.5 hours. As a result, a hotspot having a maximum temperature was observed at a site located 470 mmapart from the end of the raw material gas inlet side of a catalystlayer, wherein AT at the maximum temperature was 31° C. In addition, therate of reaction of propylene was 98.6%, the selectivity factor ofacrolein was 88.1%, the selectivity factor of acrylic acid was 5.8%, andthe yield of acrolein and acrylic acid was 92.6%.

COMPARATIVE EXAMPLE 7

[0069] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the temperature of a heating medium bath waselevated to 310° C. without passing the passing gas through a catalystlayer after elevating the temperature, and except that thereafter a rawmaterial gas was immediately passed through the catalyst layer. As aresult, a hot spot having a maximum temperature was observed at a sitelocated 400 mm apart from the end of the raw material gas inlet side ofthe catalyst layer, wherein ΔT at the maximum temperature was 41° C. Inaddition, the rate of reaction of propylene was 98.9%, the selectivityfactor of acrolein was 86.5%, the selectivity factor of acrylic acid was5.0%, and the yield of acrolein and acrylic acid was 90.5%.

COMPARATIVE EXAMPLE 8

[0070] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the time for passing the passing gas afterelevating the temperature was changed to ten minutes. As a result, a hotspot having a maximum temperature was observed at a site located 400 mmapart from the end of the raw material gas inlet side of the catalystlayer, wherein ΔT at the maximum temperature was 40° C. In addition, therate of reaction of propylene was 98.7%, the selectivity factor ofacrolein was 86.7%, the selectivity factor of acrylic acid was 5.1%, andthe yield of acrolein and acrylic acid was 90.6%.

COMPARATIVE EXAMPLE 9

[0071] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 4.5% byvolume of propylene, 12% by volume of oxygen, 10% by volume of watervapor and 73.5% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 400 mm apart from theend of the raw material gas inlet side of the catalyst layer, wherein ΔTat this maximum temperature was 41° C. In addition, the rate of reactionof propylene was 98.9%, the selectivity factor of acrolein was 86.5%,the selectivity factor of acrylic acid was 5.0%, and the yield ofacrolein and acrylic acid was 90.5%.

COMPARATIVE EXAMPLE 10

[0072] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the composition of the passing gas afterelevating the temperature was changed to the one comprising 0.6% byvolume of propylene, 8% by volume of oxygen, 15% by volume of watervapor and 76.4% by volume of nitrogen. As a result, a hot spot having amaximum temperature was observed at a site located 400 mm apart from theend of the raw material gas inlet side of the catalyst layer, wherein ΔTat this maximum temperature was 40° C. In addition, the rate of reactionof propylene was 98.7%, the selectivity factor of acrolein was 86.7%,the selectivity factor of acrylic acid was 5.1%, and the yield ofacrolein and acrylic acid was 90.6%.

COMPARATIVE EXAMPLE 11

[0073] An oxidation reaction was carried out in a similar manner to thatin Example 1, except that the composition of the gas as passed when thetemperature of a heating medium bath was elevated to 310° C. was changedto the one comprising 2% by volume of propylene, 8% by volume of oxygen,15% by volume of water vapor and 75% by volume of nitrogen. As a result,a hot spot having a maximum temperature was observed at a site located550 mm apart from the end of the raw material gas inlet side of acatalyst layer, wherein ΔT at this maximum temperature was 20° C. Inaddition, the rate of reaction of propylene was 94.7%, the selectivityfactor of acrolein was 88.0%, the selectivity factor of acrylic acid was5.6%, and the yield of acrolein and acrylic acid was 88.6%. From theresults, it is considered that the catalyst was poisoned when thetemperature thereof was elevated, because ΔT at the hot spot wasdecreased as compared to the one in Example 1 while the rate of reactionof propylene also was decreased.

EXAMPLE 8

[0074] To 1000 parts of water, 500 parts of ammonium paramolybdate, 12.3parts of ammonium paratungstate and 1.4 parts of potassium nitrate wereadded, heated and agitated, and thereafter a solution in which 4.1 partsof 85% by mass phosphoric acid is dissolved in 100 parts of water wasadded thereto, and further heated and agitated (Liquid C). Aside fromthis, to 850 parts of water, 50 parts of nitric acid of 60% by mass wereadded and homogenized, and then 114.5 parts of bismuth nitrate wereadded thereto and dissolved. To the mixture, 143.0 parts of ferricnitrate, 309.0 parts of cobalt nitrate, 7.0 parts of zinc nitrate, 3.2parts of silver nitrate and 6.1 parts of magnesium nitrate weresequentially added and dissolved (Liquid D). Liquid D was added toLiquid C to form a slurry, and then heated and agitated, so that most ofwater was evaporated. The resultant caked matter was dried at atemperature of 130° C., and then calcined at a temperature of 300° C. inan atmosphere of air for a period of one hour, and pulverized. To 100parts of the resultant pulverized product, 2 parts of graphite wereadded and mixed, which were then formed into rings having an outerdiameter of 4 mm, an inner diameter of 2 mm and a length of 4 mm byusing a tablet forming machine. This formed tablet product was calcinedat a temperature of 500° C. in an atmosphere of air for a period of sixhours, whereby Catalyst 2 was obtained. The elementary composition ofCatalyst 2 comprisedMo₁₂W_(0.2)Bi₁Fe_(1.5)P_(0.15)Ag_(0.08)Co_(4.5)Zn_(0.1)Mg_(0.1)K_(0.06),as an atomic ratio except oxygen.

[0075] The temperature of a heating medium bath of a tubular type offixed bed steel reactor having an inner diameter of 25.4 mm as providedwith the heating medium bath was set to a temperature of 180° C., andthe inlet side for raw material gas was filled with a mixture of 620 mlof Catalyst 2 and 130 ml of a spherical alumina having an outer diameterof 5 mm, while the outlet side was filled with 750 ml of Catalyst 2,wherein the length of a catalyst layer was 3005 mm.

[0076] The heating medium bath temperature was elevated to a temperatureof 310° C. at a rate of 50° C./hour, while a gas comprising 9% by volumeof oxygen, 10% by volume of water vapor and 81% by volume of nitrogenwas passed through this catalyst layer at a space velocity of 240hour⁻¹.

[0077] Then, with the heating medium bath temperature maintained at atemperature of 310° C., a gas comprising 2% by volume of propylene, 8%by volume of oxygen, 15% by volume of water vapor and 75% by volume ofnitrogen was passed through the catalyst layer at a space velocity of1000 hour⁻¹ for a period of three hours.

[0078] Subsequently, with the heating medium bath temperature maintainedat a temperature of 310° C., a raw material gas comprising 5% by volumeof propylene, 12% by volume of oxygen, 10% by volume of water vapor and73% by volume of nitrogen was passed through the catalyst layer at areaction temperature (i. e., a heating medium bath temperature) of 310°C. at a space velocity of 1000 hours⁻¹. When the temperatures of thecatalyst layer were measured at this time, a hot spot having a maximumtemperature was observed at a site located 550 mm apart from the end ofthe inlet side for the raw material gas, wherein ΔT at the maximumtemperature was 32° C. In addition, the rate of reaction of propylenewas 99.0%, the selectivity factor of acrolein was 89.0%, the selectivityfactor of acrylic acid was 6.2%, and the yield of acrolein and acrylicacid was 94.2%.

COMPARATIVE EXAMPLE 12

[0079] An oxidation reaction was carried out in a similar manner to thatin Example 4, except that the temperature of a heating medium bath waselevated to 310° C. without passing the passing gas after elevating thetemperature, and except that thereafter a raw material gas wasimmediately passed through the catalyst layer. As a result, a hot spothaving a maximum temperature was observed at a site located 450 mm apartfrom the end of the raw material gas inlet side of the catalyst layer,wherein ΔT at the maximum temperature was 44° C. In addition, the rateof reaction of propylene was 99.4%, the selectivity factor of acroleinwas 86.5%, the selectivity factor of acrylic acid was 5.9%, and theyield of acrolein and acrylic acid was 91.8%.

Industrial Applicability

[0080] According to the method for producing methacrolein and/ormethacrylic acid by subjecting isobutylene and/or tertiary butanol to avapor-phase catalytic oxidation with molecular oxygen in the presence ofa solid oxidation catalyst in a tubular type of fixed bed reactor, ofthe present invention, a temperature of a hot-spot zone can besufficiently controlled, whereby methacrolein and methacrylic acid canbe produced with a high yield.

[0081] Furthermore, the use of the compound oxide represented by theabove-mentioned formula (1) as the solid oxidation catalyst furtherenhances the yield of methacrolein and methacrylic acid.

[0082] According to the method for producing acrolein and/or acrylicacid by subjecting propylene to a vapor-phase catalytic oxidation withmolecular oxygen in the presence of a solid oxidation catalyst in atubular type of fixed bed reactor, of the present invention, atemperature of a hot-spot zone can be sufficiently controlled, wherebyacrolein and acrylic acid can be produced with a high yield.

[0083] Furthermore, the use of the compound oxide represented by theabove-mentioned formula (2) as the solid oxidation catalyst furtherenhances the yield of acrolein and acrylic acid.

1. A method for producing methacrolein and/or methacrylic acid bypassing a raw material gas comprising isobutylene and/or tertiarybutanol and oxygen through a catalyst layer in a tubular type of fixedbed reactor which is filled with a solid oxidation catalyst, whichcomprises passing a gas comprising isobutylene and/or tertiary butanolin a concentration lower than that of said raw material gas, and oxygenthrough said catalyst layer for a period of one hour or more prior topassing said raw material gas through said catalyst layer.
 2. A methodfor producing methacrolein and/or methacrylic acid, which comprises:filling a tubular type of fixed bed reactor with a solid oxidationcatalyst; elevating a temperature of the resultant catalyst layer to arange of 250° C. to 400° C. while passing a gas including oxygen,nitrogen, water vapor and 0 to 0.5% by volume of isobutylene and/ortertiary butanol through said catalyst layer; passing a gas including 1to 3.8% by volume of isobutylene and/or tertiary butanol, 7 to 16% byvolume of oxygen and 5 to 50% by volume of water vapor through saidcatalyst layer at a temperature of 250° C. to 400° C. for a period ofone hour or more; and thereafter passing a raw material gas including 4to 9% by volume of isobutylene and/or tertiary butanol, 7 to 16% byvolume of oxygen and 5 to 50% by volume of water vapor through saidcatalyst layer at a temperature of 250° C. to 400° C.
 3. The method forproducing methacrolein and/or methacrylic acid according to claim 1 or2, wherein said solid oxidation catalyst is a compound oxide representedby the following formula (1):Mo_(a)Bi_(b)Fe_(c)A_(d)X_(e)Y_(f)Z_(g)O_(h)  (1) wherein Mo, Bi, Fe andO represent molybdenum, bismuth, iron and oxygen, respectively; Arepresents nickel and/or cobalt; X represents at least one elementselected from the group consisting of magnesium, zinc, chromium,manganese, tin and lead; Y represents at least one element selected fromthe group consisting of phosphorus, boron, sulfur, tellurium, silicon,germanium, cerium, niobium, titanium, zirconium, tungsten and antimony;Z represents at least one element selected from the group consisting ofpotassium, sodium, rubidium, cesium and thallium; and each of a, b, c,d, e, f, g and h represents an atomic ratio of each element, wherein0.1≦b≦5, 0.1≦c≦5, 1≦d ≦12, 0≦e≦10, 0≦f≦10 and 0.01≦g≦3 when a=12, and hmeans an atomic ratio of oxygen necessary to satisfy the atomic valenceof each of said elements.
 4. A method for producing acrolein and/oracrylic acid by passing a raw material gas comprising propylene andoxygen through a catalyst layer in a tubular type of fixed bed reactorwhich is filled with a solid oxidation catalyst, which comprises passinga gas comprising propylene in a concentration lower than that of saidraw material gas, and oxygen through said catalyst layer for a period ofone hour or more prior to passing said raw material gas through saidcatalyst layer.
 5. A method for producing acrolein and/or acrylic acid,which comprises: filling a tubular type of fixed bed reactor with asolid oxidation catalyst; elevating a temperature of the resultantcatalyst layer to a range of 250° C. to 400° C. while passing a gasincluding oxygen, nitrogen, water vapor and 0 to 0.5% by volume ofpropylene through said catalyst layer; passing a gas including 1 to 3.8%by volume of propylene, 7 to 16% by volume of oxygen and 5 to 50% byvolume of water vapor through said catalyst layer at a temperature of250° C. to 400° C. for a period of one hour or more; and thereafterpassing a raw material gas including 4 to 9% by volume of propylene, 7to 16% by volume of oxygen and 5 to 50% by volume of water vapor throughsaid catalyst layer at a temperature of 250° C. to 400° C.
 6. The methodfor producing acrolein and/or acrylic acid according to claim 4 or 5,wherein said solid oxidation catalyst is a compound oxide represented bythe following formula (2):Mo_(a′)Bi_(b′)Fe_(c′)A′_(d′)X′_(e′)Y′_(f′)Z′_(g′)Si_(h′)O_(i)  (2)wherein Mo, Bi, Fe, Si and O represent molybdenum, bismuth, iron,silicon and oxygen, respectively; A′ represents nickel and/or cobalt; X′represents at least one element selected from the group consisting ofmagnesium, zinc, chromium, manganese, tin, strontium, barium, copper,silver and lead; Y′ represents at least one element selected from thegroup consisting of phosphorus, boron, sulfur, tellurium, aluminum,gallium, germanium, indium, lanthanum, cerium, niobium, tantalum,titanium, zirconium, tungsten and antimony; Z′ represents at least oneelement selected from the group consisting of potassium, sodium,rubidium, cesium and thallium; each of a′, b′, c′, d′, e′, f′, g′, h′and i represents an atomic ratio of each element, wherein 0.01≦b′≦5,0.01≦c′≦5, 1≦d′≦12, 0≦e′≦10, 0≦f′≦10, 0.001≦g′≦3 and 0≦h′≦20 when a′=12,and i means an atomic ratio of oxygen necessary to satisfy the atomicvalence of each of said elements.